This invention relates to monitoring devices and in particular to devices for monitoring the separation between two relatively movable parts.
With many kinds of machinery it is often desirable that some indication be provided that the separation between two relatively moving parts has reduced by more than a given extent. In the case of a turret crane for example, the crane jib structure is mounted on a platform which is rotatably carried from a base by means of a ring bearing. Monitoring the extent to which the separation decreases during rotation between the base and platform provides an indication of the state of wear in the ring bearing.